As disclosed in Japanese Patent Unexamined Publication No. 2-103714, in a conventional magnetic head slider, a recording-reproducing element portion has an alumina film which is formed as a base film for forming and holding magnetic poles, a coil, a magneto-resistance effect element and so on, or as a protective film which is effective in an element-forming process so that the magnetic poles, the coil, the magneto-resistance effect element and so on will not be damaged during process steps and during handling. As described in the above publication, this alumina film can be relatively easily worn and damaged upon sliding contact with a medium. Therefore, in the above conventional example, the area of exposure of this alumina film to the sliding surface is kept to a minimum so as to reduce the probability of sliding contact of this alumina film with the medium. Therefore, this alumina film does not function as a sliding protective film for sliding contact with the medium, but functions as the base film, which is part of the element-forming members, or as the protective film effective in the element-forming process.
Recently, the frequency of contact between a slider and a medium increases with a reduced flying height of the slider and also with the practical use of a contact-recording system in which a slider is always held in contact with the medium, and besides with the practical use of magneto-resistance effect elements having poor sliding durability, the enhancement of the sliding durability can not be expected even if the area of the process protective film is reduced as in the above conventional example, and there has been encountered a problem that the element portion travel surface is worn and damaged.
Therefore, a sliding protective film, constituted by a multi-layer film made of silicon, carbon and so on, has been formed on a slider travel surface, a flying rail surface and an element portion travel surface (hereinafter, the surfaces in this direction will be referred to as "travel surface") so as to protect these surfaces from sliding contact.
In order to achieve a high-density recording design of a magnetic disk unit, it is necessary to make the distance (this distance will hereinafter be referred to as "magnetic spacing") between the element portion travel surface and a magnetic layer of the medium very narrow. This sliding protective film is a loss for the narrowing of the magnetic spacing, and therefore the thickness of this sliding protective film has heretofore been not more than several tens of nm. However, as described above, the frequency of contact between the slider and the medium increases, and there has been encountered a problem that the sliding protective film, having the above thickness, is insufficient in durability.
Therefore, as disclosed in Japanese Patent Unexamined Publication Nos. 7-6340, 8-45022 and 8-45045, a film with a smaller thickness, made of a material having better durability, such as diamond-like carbon (DLC), has been used as a sliding protective film, but even such a material as DLC is insufficient in durability for the contact-recording system.
Generally, a sliding protective film, made of a material such as DLC, is formed or coated by a film-forming method called sputtering or CVD. In these film-forming methods, the density and durability of the formed film are enhanced in proportion to the thickness of the formed film. Particularly, in the formation of a diamond film which is the most durable, the film must undergo crystal growth, and therefore with the currently-available techniques, the practical film, having a thickness of not more than 1 .mu.m, can not be formed. Therefore, in order to further enhance the durability of the material, the thickness of the sliding protective film must be increased, which has invited a problem that this is contradictory to the narrowing of the magnetic spacing.
Further, in the formation of the diamond film, the temperature of the film, as well as the temperature of its vicinity, becomes more than 800.degree. C. In the conventional method in which the sliding protective film is formed after the recording-reproducing element is formed, the recording-reproducing element is destroyed by this temperature, and therefore diamond could not be used as the sliding protective film.
Japanese Patent Unexamined Publication Nos. 8-45022 and 8-45045 disclose a technique in which the sliding protective film is formed not only on the travel surface but also on a surface perpendicular to this travel surface so as to prevent corrosion and also to protect an edge portion of the slider. However, it is very difficult to form the film on the two surfaces continuous with each other in perpendicular relation to each other, and besides since the sliding protective film is present even at the element portion travel surface, there has been encountered a problem that this technique is not suitable for further narrowing the magnetic space.
In a method of producing the conventional magnetic head slider, the recording-reproducing elements are formed on a surface of a slider substrate by an ordinary film-forming method, and thereafter the substrate is cut into slider blocks by machining, and the sliding protective film is formed on the cut surface, again using the film-forming method. Therefore, this method has an increased number of process steps, and is complicated.
The above conventional technique has a problem that no consideration is given for satisfying the requirement for the narrowed magnetic spacing and the requirement for the enhanced sliding durability of the travel surface in a compatible manner while enhancing the performance to a higher level, and therefore the enhancement of the recording density for the future and the assurance of the reliability for an increase of the contact frequency resulting therefrom can not be achieved in a compatible manner.